DIFFUSION-WEIGHTED MR OF ACUTE CEREBRAL INFARCTION - COMPARISON OF DATA-PROCESSING METHODS

BACKGROUND AND PURPOSE: Some investigators have proposed that either c alculated diffusion trace images or apparent diffusion coefficient (AD C) maps, which require imaging with multiple diffusion sensitivities a nd/or postacquisition image processing, are essential for the accurate interpretation of diffusion-weighted images in acute stroke because o f the possible pitfalls of regional diffusion anisotropy, magnetic sus ceptibility artifacts, and confounding T2 effects, all of which alter signal on diffusion-weighted MR images. The purpose of our study was t o compare the sensitivity, specificity, and accuracy of simple, orthog onal-axis diffusion-weighted imaging for the diagnosis of early cerebr al infarction with three other sets of postacquisition-processed image s: isotropic diffusion-weighted, diffusion trace-weighted, and diffusi on trace images. METHODS: Twenty-six consecutive adult patients with s igns and symptoms consistent with a clinical diagnosis of early cortic al and/or subcortical cerebral infarction and 17 control subjects were studied with multisection, single-shot, spin-echo echo-planar diffusi on-weighted imaging at 1.5 T to generate a set of three orthogonal-axi s diffusion-weighted images. Isotropic diffusion-weighted, diffusion t race-weighted, and diffusion trace (mean ADC) images were then generat ed off-line and all four sets of images were interpreted blindly by tw o neuroradiologists. RESULTS: The average sensitivity, specificity, an d accuracy for the orthogonal-axis diffusion-weighted images were 98.1 %, 97.1%, and 97.7%, respectively. The average sensitivity, specificit y, and accuracy for isotropic diffusion-weighted images were 88.5%, 10 0%, and 93% respectively. The average sensitivity, specificity, and ac curacy for diffusion trace-weighted images were 82.7%, 73.6%, and 79.1 %, respectively. The average sensitivity, specificity, and accuracy fo r diffusion trace images were 50.0%, 85.3%, and 64.0%, respectively. C ONCLUSION: Orthogonal-axis diffusion-weighted images have the highest sensitivity and accuracy and very high specificity for early cerebral infarction. Our data contradict the contention that quantitative diffu sion maps, requiring imaging with multiple diffusion sensitivities and /or subsequent image processing, are necessary for clinical stroke ima ging.